The present invention relates to a gel electrolyte precursor, a chemical battery comprising a gel electrolyte obtained from the gel electrolyte precursor, and a method of manufacturing the chemical battery.
A nonaqueous electrolyte secondary battery, which is an example of the chemical battery, comprises an electrode group including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte held by the electrode group. Used as the positive electrode active material is, for example, a lithium-containing complex oxide. Also, the negative electrode is formed of, for example, lithium, a lithium alloy, or a carbonaceous material absorbing-desorbing lithium. On the other hand, a liquid nonaqueous electrolyte prepared by dissolving a lithium salt as an electrolyte in a nonaqueous solvent such as propylene carbonate or γ-butyrolactone is used as the nonaqueous electrolyte.
In recent years, it is required to increase the capacity of the battery, to make the battery thinner and to increase the active area of the battery in accordance with miniaturization, reduction in thickness and improvement in the performance of electronic appliances. It is proposed to use a film material such as a laminate film in place of a metal can as a vessel for housing the electrode group in an attempt to decrease the thickness of the nonaqueous electrolyte secondary battery and to make the secondary battery light in weight. In the case of using a film material, however, the liquid nonaqueous electrolyte tends to leak to the outside. Also, the distribution of the nonaqueous electrolyte within the electrode group tends to be nonuniform. As a result, a problem is generated that the cycle characteristics are lowered. In order to avoid the particular problem, it is studied to impart viscosity to the liquid nonaqueous electrolyte so as to lower the fluidity of the liquid nonaqueous electrolyte.
For example, Japanese Patent Publication (Kokoku) No. 61-23944 discloses a solid composition having an ionic conductivity, comprising an electrolyte consisting of ions of metals belonging to Group I and/or Group II of the Periodic Table, an organic high molecular weight compound having a relative dielectric constant smaller than 4, and an organic solvent having an excellent solubility in respect of the electrolyte and the organic high molecular weight compound noted above and also having a relative dielectric constant smaller than 10. It is disclosed that the solid composition having an ionic conductivity contains the electrolyte in an amount sufficient for imparting an ionic conductivity of at least about 10−10S·cm−1 to the composition and in an amount not larger than 90 mol % of the solid composition. It is also disclosed that it is desirable to use resins other than thermosetting resins as the organic high molecular weight compound. Particularly, it is disclosed that a satisfactory result can be obtained in the case of using as the organic high molecular weight compound a thermoplastic resin having a one dimensional structure such as polymethyl methacrylate.
However, the solid composition having an ionic conductivity, which is disclosed in the prior art quoted above, has an ionic conductivity of about 10-10 to 10−7S·cm−1, which is lower than that of the liquid nonaqueous electrolyte, and is not satisfactory in the electrochemical stability.